如何使用hashmap编写相同的代码

Question

How can I write the same code using hashmap or map. So that I can retrive values in a table..

        Class.forName("oracle.jdbc.driver.OracleDriver");   
        Connection con=DriverManager.getConnection("jdbc:Oracle:thin:@localhost:1521:IHDB","pummy","pummy");   

        PreparedStatement ps=con.prepareStatement("select workitemid,empname,salary from emp where product_id=? and operation_id=?");   
        ps.setInt(1,prod_id);
        ps.setInt(2,opn_id);
        ResultSet rs=ps.executeQuery();   
        System.out.println("ProdId: "+prod_id);
         System.out.println(rs);
         while(rs.next())
            {
                BigDecimal workitemid = rs.getBigDecimal(1);
                String empname=(String) rs.getString(2);
                int salary= rs.getInt(3);
              }

Answer 1

I think the structured way would be by creating Employee pojo class like below -

public class Employee{
   public BigDecimal workitemid;
   public String empName;   
   public int salary;
   <getter & setter>
}

now create a Map - Map<BigDecimal,Employee> empMap = new HashMap<>();

while(rs.next()){
   Employee emp = new Employee();
   BigDecimal workitemid = rs.getBigDecimal(1);
   emp.setWorkitemid(workitemid);
   emp.setEmpName(rs.getString(2));
   emp.setSalary(rs.getInt(3));
   map.put(workitemid, emp);
}

Answer 2

There you are.

PreparedStatement ps=con.prepareStatement("select workitemid,empname,salary from emp where product_id=? and operation_id=?");   
            ps.setInt(1,prod_id);
            ps.setInt(2,opn_id);
            ResultSet rs=ps.executeQuery();   
            System.out.println("ProdId: "+prod_id);
            Map<BigDecimal,Employee> empMap= new HashMap<BigDecimal,Employee>();
             System.out.println(rs);
             while(rs.next())
                {
                  Employee emp = new Employee();
                  emp.setWorkItemId = rs.getBigDecimal(1);
                  emp.setEmpName(rs.getString(2));
                  emp.setSalary(rs.getInt(3));
                  empMap.put(emp.getWorkItemId,emp);


                  }

    private class Employee{
      private String empName;
      private int salary;
      private BigDecimal workItemId;
     //getters and setters

    }

Answer 3

    PreparedStatement ps=con.prepareStatement("select workitemid,empname,salary from emp where product_id=? and operation_id=?");   
    ps.setInt(1,prod_id);
    ps.setInt(2,opn_id);
    ResultSet rs=ps.executeQuery();   
    System.out.println("ProdId: "+prod_id);
    System.out.println(rs);

    Map<BigDecimal, Employee> employees = new HashMap<BigDecimal, Employee>();        

    while(rs.next())
       {
           BigDecimal workitemid = rs.getBigDecimal(1);
           String empname=(String) rs.getString(2);
           int salary= rs.getInt(3);
           Employee employee = new Employee(workitemid, empname, salary);

           employees.put(workitemid , employee);
       }

 //object to hold information about an employee and to be able to use a map.
    public class Employee
    {
    private BigDecimal workitemid;
    private String empName;   
    private int salary;

    //constructor
    public Employee(BigDecimal workitemid, String empName, int salary)
    {
      this.workitemid = workitemid;
      this.empName = empName;
      this.salary = salary;
    }


    //setters and getter methods for workitemid, empName, salary.
    }